1. In a medium bowl, combine the grapefruit juice cocktail and simple syrup. Halve the orange and thinly cut 6 half moon slices. Quarter the grapefruit and cut 6 quarter moon slices.
2. Place 1 slice orange and 1 slice grapefruit up against the inside of each 6 ice pop molds, pressing to adhere to the sides.
3. Divide juice mixture between the molds. Insert ice pop sticks and freeze 4 hours, until solid. When ready to eat, run the pops under warm water for a few seconds to release from molds.
To make simple syrup, place equal parts sugar and water in a pot. Heat on medium-high just until melted. Cool before use.